Cleaning a pizza stone: what to do and what not to

Black is not dirty

A stone that has done a season is dark brown to black and uneven in colour. That is baked-in oil and charred flour, and it sits in the pores of the stone rather than on it.

That layer is useful. It makes the stone less porous and therefore less sticky, and it changes nothing about how the stone passes on heat. Virtually every professional oven looks like this inside.

Anyone trying to remove it ends up reaching for soap, wire brushes or the dishwasher, and those are precisely the three things that wreck a stone. Let it go black.

Never soap, never submerge

A pizza stone is porous and soaks up liquid like a sponge. Soap that soaks in never comes out and evaporates at the next firing. Your pizza then bakes in washing-up fumes, and you taste it.

Water without soap is almost as troublesome. A soaked stone fired up again turns the absorbed moisture into steam inside the stone, and that steam has to go somewhere. That is the crack.

If you did have to use water, let the stone dry completely for at least twenty-four to forty-eight hours before it goes back in the oven, and then warm it slowly.

• No soap, ever.
• No dishwasher, no soaking in the sink.
• Been wet? Two days of drying, then a slow warm-up.

How to actually clean it

The easiest method costs nothing: after baking, leave the oven at full temperature for another ten to fifteen minutes with the stone in it. Baked-on cheese and dough burn to ash, which you brush off dry the next day.

For whatever stays, use a scraper or a firm spatula on the cold stone, or a brush with natural bristles or brass. No wire brush: it leaves metal particles behind and damages the surface.

Fat that has soaked in, you leave. That is the layer from the paragraph above, not something to remove.

• Burning it off at high temperature is the main method.
• Brush it dry once the stone is cold.
• Scraper or spatula for what sticks, never wire wool.
• Leave grease that has soaked in. That is the seasoning, not the dirt.

Why stones crack

Nearly every crack comes from one cause: a large temperature difference in a short time. A cold stone into a hot oven, a hot stone that gets wet, or frozen dough straight onto four hundred degrees.

So always warm up with the stone inside, from cold. Never put a replacement stone into an oven that is already running, and never pour anything onto a hot stone, not even water to put out a flare-up.

Let dough come to room temperature before it meets the stone. Thirty seconds of cold dough is normal and the stone is built for it; a frozen base is not.

A stone with a hairline crack is often perfectly usable, incidentally, as long as it stays in one piece. If it still bakes evenly, there is no reason to replace it.

Storing it between seasons

Let the stone be dry and at room temperature before you store it, and store it indoors if you can, or at least under a cover. A stone that has soaked up a winter of rain and frost is a crack waiting to happen in spring.

Keep it flat, not upright against a wall. Ceramic breaks far more easily from a knock on the edge than on the face.

Start in spring with a calm first firing: warm up slowly, ten minutes at half temperature, and only then push on. That is the same rule as for a new stone.

When to replace it

Replace it if it is in two pieces, if the surface is flaking away, or if it visibly warps and no longer sits flat. All three show up in the baking.

A crack running right through, splitting the stone into two moving halves, gives a seam that dough sinks into and heat comes through differently. That is the point to replace.

Discolouration, stains and an uneven black layer are not reasons. They come with the territory, and a stone that looks like that usually bakes better than a new one.

• In two pieces, flaking or warped: replace.
• Black, stained or hairline-cracked: keep.